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MD3002 > salivary and gastric secretions > Flashcards

salivary and gastric secretions Flashcards

1
Q

what secretions are added to the lumen of the GI tract (exocrine)

A

saliva
gastric acid and secretions
pancreatic secretions
bile

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2
Q

describe the characteristics of saliva

A

high bicarbonate
high potassium
hypotonic
contains alpha amylase and lingual lipase

1 L per day

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3
Q

what factors increase salivary secretion

A

primarily parasympathetic but also sympathetic

No hormonal control

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4
Q

what factors decrease secretion

A

sleep
dehydration
atropine

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5
Q

what is the function of saliva

A

Initial digestion of starches and lipids
Dilution and buffering of ingested foods
Lubrication of ingested foods with mucous (mucin)

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6
Q

describe the function of the parotid glands

A

• Serous cells secreting an aqueous fluid composed of water,
ions and enzymes

very high blood flow

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7
Q

what makes up mucin

A

glycoprotein for lubrication

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8
Q

what do acinar cells produce

A

an initial
isotonic saliva composed of
water, ions, enzymes and
mucus

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9
Q

what do myoepithelial cells do

A

stimulated by neural input to eject saliva

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10
Q

what do ductal cells do

A

modify the initial
saliva by altering electrolyte
concentrations

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11
Q

how is saliva modified

A 
– Absorption of Na+ and Cl-
– Secretion of K+ and HCO-
3
– Becausemore NaCl is absorbed
than KHCO3 secreted there is net
absorption of solute so hypotonic
– Low water permeability of ductal
cells means that the final saliva is
hypotonic
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12
Q

what substances are secreted by the acinar cells

A 
amylase
Lingual lipase-digestion of lipids
Mucus-lubricant
Kallikrein
enzymatic cleavage of kininogen to bradykinin (potent
vasodilator)
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13
Q

how does neural stimulation affect the salivary glands

A

increased saliva
production, HCO-
3 production, enzyme secretion and
myoepithelial cell contraction

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14
Q

what substances digest protein

A

HCl and pepsinogen

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15
Q

what is the function of intrinsic factor

A

vitamin B12 absorption in the ileum

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16
Q

what is the function of mucus

A

protects mucosa and lubrications

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17
Q

what increases secretion of HCl

A

gastrin

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18
Q

what increases and decreases secretion of pepsinogen

A

acetylcholine

chyme in duodenum

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19
Q

what increases secretion of intrinsic factor

A

histamine and parasympathetic NS

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20
Q

what decreases secretion of intrinsic factor

A

Somatostatin
Atropine
Cimetidine
Omeprazole

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21
Q

where are stomach parietal cells found

A

body

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22
Q

where are chief cells found

A

body

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23
Q

where are G cells found

A

antrum

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24
Q

what are invaginations of the stomach called

A

gastric glands

they increase surface area

25
Q

describe the layers of the stomach (inside to out)

A 
mucosa and epithelia 
lamina propria
muscularis mucosae
submucosa
muscularis externa

also submucosal plexus and myenteric plexus

26
Q

name the cells in an oxyntic (gastric) gland

A

surface epithelium
mucous neck cells
parietal cells
peptic/chief cells

27
Q

what cells release HCl and intrinsic factor

A

oxyntic/ parietal cells

28
Q

what cells release pepsinogen

A

chief cells aka peptic cells

29
Q

what pH is the stomach

A

1-2

30
Q

what is responsible for conversion of pepsinogen to pepsin

A

low pH

31
Q

what is carbonic anhydrase

A

CO2 + H2O > carbonic acid

32
Q

how is HCl secreted through the apical membrane

A

– H+ is secreted into the lumen via the H+-K+ ATPase

– Cl- follows by diffusion through an apical channel

33
Q

describe the events at the basolateral surface in order to secrete HCl

A

bicarbonate ion is exchanged for Cl- via an exchanger (no ATP needed)

Na+ is swapped for K+ using ATP

34
Q

what is the cephalic phase of HCl release

A

30% of secretion
– Smell, taste, chewing, swallowing, conditioned reflex
in anticipation of food

  • Direct stimulation of the parietal cells by the vagus
  • Indirect stimulation of the parietal cells by gastrin
35
Q

what peptide stimulates gastrin release from G cells

A

Vagal gastrin releasing peptide (GRP)

this enters the circulation and stimulates parietal cells

36
Q

what causes the gastric phase of HCl secretion

A

60% of secretion
– Distension of the stomach and the presence of
breakdown products of proteins, amino acids and
small peptides in the stomach

37
Q

how does distension lead to HCl release

A

– direct vagal stimulation of parietal cells
– indirect stimulation via gastrin
– local reflexes in the antrumthat stimulate gastrin
release

38
Q

what neurotransmitter is responsible for vagal activation of parietal cells via the direct pathway

A

ACh

39
Q

what is the indirect vagal pathway

A

Vagal stimulated release of gastrin fromG cells (byGRP neuropeptide transmitter )

40
Q

how do amino acids and peptides stimulate Hcl release

A

they cause gastrin to be released

41
Q

what is the intestinal phase of HCl secretion

A

10% of secretion
– presence of breakdown products of proteins in the
duodenum

42
Q

what messengers are used in vagal stimulation of parietal cells

A

ACh and IP3/ Ca2+

muscarinic 3 receptors on parietal cells

43
Q

how does histamine stimulate Hcl secretion

A

secreted by Enterochromaffin
like cells (ECL) in the
gastric mucosa

Diffuses to and
binds to H2
receptors on
parietal cells

second messenger is cyclic AMP

44
Q

what receptors does gastrin bind to on parietal cells

A

CCKB
receptors

IP3/Ca2+ is the second messenger

45
Q

what does somatostatin do

A

inhibits Hcl secretion

– Direct pathway – binds to receptors on parietal cells and
inhibits adenylate cyclase via Gi protein
– Indirect pathway – inhibits histamine release from ECL
cells and gastrin release from G cells

46
Q

what causes secretion of pepsinogen from chief and mucous cells

A

vagal stimulation and H+ triggers local reflexes which stimulate chief cells

47
Q

what causes pernicious anaemia

A

lack of intrinsic factor

48
Q

what cells release mucoprotein containing intrinsic factor

A

parietal cells

49
Q

what is a gastrinoma

A

a tumor in the pancreas or duodenum that secretes excess of gastrin leading to ulceration in the duodenum, stomach and the small intestine. There is hypersecretion of the HCl acid into the duodenum, which causes the ulcers.

also causes hypertrophy and inactivation of pancreatic lipases

50
Q

how many lumbar veins are there

A

4 joining the IVC and one joining the common iliac

51
Q

what do the sublingual glands produce

A

mucus

52
Q

what is cimetidine

A

histamine 2 antagonist that inhibits stomach acid production

used in heart burn and peptic ulcers

53
Q

what is omeprazole

A

PPI

GERD and peptic ulcers not heartburn

54
Q

what is zollinger ellison syndrome

A

gastrin secreting tumour in the pancreas

55
Q

what is the difference between pepsin and trypsin

A

pepsin is produced in the stomach and trypsin is made in the pancreas

56
Q

where does omeprazole act

A

H/K atp ase

57
Q

where does cimetidine act

A

H2 receptors

58
Q

where is pepsinogen secreted from

A

cheif cells

MD3002 (56 decks)

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